Pathological findings on examination of full-thickness rectal tissue from all patients with megarectum
| Finding | n (%) | Notes |
| Melanosis | 0/33 (0) | |
| Fibrosis | 30/35 (85.7) | Focal submucosal only: 8 Submucosal and periplexus: 4 Submucosal and muscularis propria: 2 Submucosal, periplexus and muscularis propria: 10 Other combinations: 6 |
| Elastosis | 19/33 (57.6) 1 site: 8 2 sites: 6 3 sites: 5 | Submucosal only: 1* Periplexus only: 2 Muscularis propria only: 4† Serosa only: 1 Submucosa and muscularis propria: 2 Submucosa and periplexus: 1 Periplexus and muscularis propria: 1‡ Periplexus and serosa: 1 Muscularis propria and serosa: 1 Muscularis mucosae, submucosa and muscularis propria: 1 Submucosa, periplexus and muscularis propria: 2 Submucosa, muscularis propria and serosa: 2 |
| Neuronal abnormalities | 6/35 (17.1) | Degenerative or inflammatory neuropathy: 0 Hypoganglionosis: 2 Duplicated plexus: 3 Single ectopic ganglion: 1 |
| Muscular abnormalities | Abnormal muscle layers: 14/35 (40.0) | Degenerative or inflammatory myopathy: 0 Submucosal metaplasia: 8 Duplication of circular muscle layer: 3 Partial duplication longitudinal muscle layer: 2 Grossly thinned: 1§ |
| Muscle hypertrophy: 27/35 (77.1) | Hypertrophy circular muscle layer only: 2 Hypertrophy both muscle layers: 25 | |
| Decreased interstitial cells of Cajal | 6/27 (22.2) | Qualitative assessment: only gross reductions reported |
| Polyglucosan bodies | 15/32 (46.9) | Present on single section: 6 Present on multiple sections: 9 |
*Predominantly around the submucosal vessels.
†Includes one patient with elastosis confined to partial extra muscle layer.
‡With granulomatous response to elastin fibres.
§Appearances suggest developmental abnormality.